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Genetically-modified mosquito designed to avoid malaria spread

A model for a genetically-modified mosquito that produces malaria-combating antibodies and fails to transmit the disease has been developed.

The modified Anopheles stephensi mosquito, a common carrier of malaria in India and the Middle East, would release antibodies that stall the development of the Plasmodium falciparum parasite or terminate it completely. The mosquito would also be unable to transmit the parasite by biting, making it a viable alternative to the malaria vaccine solution. "This is the first model of a malaria vector with a genetic modification that can potentially exist in wild populations and be transferred through generations without affecting their fitness," said Anthony James, lead author on the study and professor of microbiology and molecular genetics and molecular biology and biochemistry at the University of California Irvine.

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The study, which is due to be published in the Proceedings of the National Academy of Sciences, demonstrates how a gene found in mice inspired the model. Mice infected with malaria release Plasmodium falciparum-killing antibodies -- after modifying the molecular make-up of the mouse immune response system James and his team at UCI and the Pasteur Institute in Paris engineered genes that would replicate the process in mosquitos. In mosquitoes, the parasites would either not get the chance to develop into a strain harmful to humans, or would be killed off entirely by the antibodies. They claim the technique can be repeated with many different species, making it a viable option for tackling malaria worldwide. "This blocking process within the insect that carries malaria can help significantly reduce human sickness and death," said James, who has also released past studies on genetically-modified mosquitos that may help combat dengue fever. First, however, the team need to overcome certain stumbling blocks to begin testing the theory. "It will take another year or so to make something eligible for field trials," James told Wired.co.uk. "However, all ethical, social and legal concerns over the use of a genetically-engineered mosquito in a country willing to give it a trial also will have to be satisfied. Meeting these concerns requires significant community engagement and intellectual and emotional ownership of the technology by the end-users and stakeholders. I don't know how long this could take, but it won't be fast."

News of the UCI research follows similar findings by a team at the Johns Hopkins Malaria Research Institute. The team, led by George Dimopoulos of the department of molecular microbiology and immunology, demonstrated how the Anopheles mosquito could have its immune system altered to prevent the transfer of the malaria parasite to humans. Their genetically-modified mosquitoes produce high levels of the Re12 protein during feeding, a protein that acts within the mosquito's own immune system to attack the parasite.

The study differs here in that no new gene is actually introduced into the Anopheles. Their own genes are instead modified, their parasite-fighting abilities magnified. "The immune system of the Anopheles mosquito is capable of killing a large proportion -- but not all -- of the disease-causing parasites that are ingested when the mosquito feeds on an infected human," said Dimopoulos. According to the study, the modified mosquitos' health equalled that of an ordinary one, meaning it could compete in the wild, though no one can predict how they will fare outside of the lab. "We've taken a giant step toward the development of new mosquito strains that could be released to limit malaria transmission, but further studies are needed to render this approach safe and fail-proof," said Dimopoulos.

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The safe release of genetically-modified insects into the wild will be an issue down the line, and it is not known how effective the new strain's ability to deplete the ordinary mosquito population will be.

According to the World Health Organisation's 2011 malaria report, there were around 216 million cases of the disease in 2010 and an estimated 655 000 deaths. The majority of the deaths were among children in Africa.